Security and surveillance cameras are widely used nowadays. Generally, these cameras fall under three categories: analog cameras, digital cameras and IP cameras. The image and video data captured by these cameras are typically transmitted over a long distance (e.g., 300-500 feet of a coaxial cable or a twisted pair) to a receiver for monitoring, storage, display and/or further transmission. Depending on the type of cameras, the processing of the captured video data before transmission to the receiver varies. For example, the IP camera may involve reformatting the video data into IP packets which will cause further delay. Some IP camera further employs compression process to reduce the amount of video data that needs to be transmitted over a channel with limited bandwidth. Some digital cameras instead send the full resolution of the captured data without compression thus providing almost real time transmission of the data. Regardless of the signal pre-processing schemes actually employed, the data all suffer from channel loss while being transmitted over the long distance of a transmission line.
Various methods and apparatuses have been proposed to address the quality deterioration issue. One known approach is to send equalization reference signals together with the video signal and use received reference signal(s) to determine the channel response and then compensate for the channel loss on the receiver end. For example, the Chinese patent application with Publication Number CN104836988 discloses exchanging transmission protocol and equalization reference signal patterns during the vertical blanking interval (VBI) of an analog video signal transmitted from camera side to the receiver side to improve the transmission of a high-definition video signal over a long distance.
However, the scheme disclosed in the application above has a few shortcomings. For example, each data bit of the protocol or control data that is transmitted during the vertical blanking period is encapsulated by both a beginning signal and an end signal. This overhead significantly reduces the available time for transmitting actual protocol data given that the duration of a VBI is fixed for a given video resolution format. In addition, the Nextchip scheme teaches transmitting a complex pattern of equalization reference signals during the vertical blanking interval for downstream equalization in the receiver. The transmission of this complex pattern of equalization reference signals is unnecessary and further reduces the utilization of the VBI.
Accordingly, there remains a need in the art for a solution that addresses the problems discussed above among others.